scholarly journals Flow and internal structure of a rock glacier

1997 ◽  
Vol 43 (144) ◽  
pp. 238-244
Author(s):  
Roger F. Elconin ◽  
Edward R. LaChapelle
Keyword(s):  
Cross Section ◽  
Transverse Cross Section ◽  
Center Line ◽  
Transverse Compression ◽  
Rock Glacier ◽  
Planar Structures ◽  
Glacier Ice ◽  
Rock Glaciers ◽  
Ice Content ◽  
Longitudinal Structures

AbstractExposure of a full transverse cross-section of the terminus of Fireweed rock glacier, Wrangell Mountains, Alaska, revealed a thin layer of unconsolidated debris mantling a consolidated mélange of ice and rock. The main rock glacier is fed by three tributaries; at the terminus, contacts between the three are sharply defined. Ice content is >50% by volume. Bubble foliation and crystal morphologies of the ice matrix are similar to those reported from glacier ice. Folded ice-rich strata and lenses, foliation planes, and the long-intermediate axial planes of tabular-shaped englacial clasts dip sleeply toward the center line of the rock glacier. The planar structures generally parallel the steep walls of the gorge containing the trunk stream. These steeply dipping, longitudinal structures appear to result from transverse compression where the tributaries converge and the trunk stream narrows down-valley.Bergschrund-like and moulin-like features at the heads of the middle and west tributaries, respectively, exposed admixed ice and rock similar to that of the terminus but lacking the well-developed flow texture. Talus from the unstable cirque headwall and polygenetic ice both accumulate at the base of the headwall and nourish the tributary rock glaciers.

scholarly journals Flow and internal structure of a rock glacier

1997 ◽  
Vol 43 (144) ◽  
pp. 238-244 ◽  
Author(s):  
Roger F. Elconin ◽  
Edward R. LaChapelle
Keyword(s):  
Cross Section ◽  
Transverse Cross Section ◽  
Center Line ◽  
Transverse Compression ◽  
Rock Glacier ◽  
Planar Structures ◽  
Glacier Ice ◽  
Rock Glaciers ◽  
Ice Content ◽  
Longitudinal Structures

AbstractExposure of a full transverse cross-section of the terminus of Fireweed rock glacier, Wrangell Mountains, Alaska, revealed a thin layer of unconsolidated debris mantling a consolidated mélange of ice and rock. The main rock glacier is fed by three tributaries; at the terminus, contacts between the three are sharply defined. Ice content is >50% by volume. Bubble foliation and crystal morphologies of the ice matrix are similar to those reported from glacier ice. Folded ice-rich strata and lenses, foliation planes, and the long-intermediate axial planes of tabular-shaped englacial clasts dip sleeply toward the center line of the rock glacier. The planar structures generally parallel the steep walls of the gorge containing the trunk stream. These steeply dipping, longitudinal structures appear to result from transverse compression where the tributaries converge and the trunk stream narrows down-valley.Bergschrund-like and moulin-like features at the heads of the middle and west tributaries, respectively, exposed admixed ice and rock similar to that of the terminus but lacking the well-developed flow texture. Talus from the unstable cirque headwall and polygenetic ice both accumulate at the base of the headwall and nourish the tributary rock glaciers.

scholarly journals Ice content and interannual water storage changes of an active rock glacier in the dry Andes of Argentina

2020 ◽  
Author(s):  
Christian Halla ◽  
Jan Henrik Blöthe ◽  
Carla Tapia Baldis ◽  
Dario Trombotto ◽  
Christin Hilbich ◽  
...  
Keyword(s):  
Seismic Refraction ◽  
Water Storage ◽  
Field Studies ◽  
High Mountain ◽  
Rock Glacier ◽  
Mountain Catchment ◽  
Rock Glaciers ◽  
Ice Content ◽  
Surface Ice ◽  
Water Contents

Abstract. The quantification of volumetric ice and water contents in active rock glaciers is necessary to estimate their role as water stores and contributors to runoff in dry mountain catchments. In the semi-arid to arid Andes of Argentina, active rock glaciers potentially constitute important water reservoirs due to their widespread distribution. Here however, water storage capacities and their interannual changes have so far escaped quantification in detailed field studies. Volumetric ice and water contents were quantified using a petrophysical four-phase model (4PM) based on complementary electrical resistivities (ERT) and seismic refraction tomographies (SRT) in different positions of Dos Lenguas rock glacier in the Upper Agua Negra basin, Argentina. We derived vertical and horizontal surface changes of the Dos Lenguas rock glacier, for the periods 2016–17 and 2017–18 using drone-derived digital elevation models (DEM). Interannual water storage changes of −36 mm yr−1 and +27 mm yr−1 derived from DEMs of Difference (DoD) for the periods 2016–17 and 2017–18, respectively, indicate that significant amounts of annual precipitation rates can be stored in and released from the active rock glacier. Heterogeneous ice and water contents show ice-rich permafrost and supra-, intra- and sub-permafrost aquifers in the subsurface. Active layer and ice-rich permafrost control traps and pathways of shallow ground water, and thus regulate interannual storage changes and water releases from the active rock glacier in the dry mountain catchment. The ice content of 1.7–2.0 × 109 kg in the active Dos Lenguas rock glacier represents an important long-term ice reservoir, just like other ground ice deposits in the vicinity, if compared to surface ice that covers less than 3 % of the high mountain catchment.

Rock glaciers : II models and mechanisms

1992 ◽  
Vol 16 (2) ◽  
pp. 127-186 ◽  
Author(s):  
W. Brian Whalley ◽  
H. Elizabeth Martin
Keyword(s):  
Morphological Characteristics ◽  
Sensu Stricto ◽  
Good Evidence ◽  
Conclusive Evidence ◽  
Creep Model ◽  
Rock Glacier ◽  
Side Rock ◽  
Glacier Ice ◽  
Rock Glaciers ◽  
Single Flow

This second part of a review deals with the mechanisms of rock glacier formation and flow. The presence of a copious debris supply is important in all models, although the source of ice necessary for deformation of the debris is in dispute. Evidence for the three main models: permafrost creep, debris-covered glaciers and talus deformation (rockslide), are reviewed. Seismic and resistivity evidence suggests a nonglacial (permafrost) origin where such measurements have been made. There is also good evidence that glacier ice can be seen and its extent determined in other examples. Morphological characteristics are presented; in some cases they seem to be applicable to the permafrost creep model but can also be explained by the debris-covered glacier model. The consequences of both these models are discussed in the light of the appropriate flow law models. Several different ways in which talus deformation have been suggested and these can be applied in some cases. Because of confusion in the designation of 'valley side rock glaciers' these are here termed 'protalus lobes'. The origin of these features is still problematical and may not be the same as for rock glaciers sensu stricto. It is argued that there is still no conclusive evidence for a single flow mechanism for all the features ascribed as rock glacier or protalus lobes.

scholarly journals Modelling rock glacier velocity and ice content, Khumbu and Lhotse Valleys, Nepal

2021 ◽  
Author(s):  
Yan Hu ◽  
Stephan Harrison ◽  
Lin Liu ◽  
Joanne Laura Wood
Keyword(s):  
Current Knowledge ◽  
Slope Angle ◽  
Water Volume ◽  
Active Layer Thickness ◽  
Rock Glacier ◽  
Average Value ◽  
Mountain Glaciers ◽  
Rock Glaciers ◽  
Glacier Velocity ◽  
Ice Content

Abstract. Rock glaciers contain significant amount of ground ice and serve as important freshwater resources as mountain glaciers melt in response to climate warming. However, current knowledge about ice content in rock glaciers has been acquired mainly from in situ investigations in limited study areas, which hinders a comprehensive understanding of ice storage in rock glaciers situated in remote mountains and over local or regional scales. In this study, we develop an empirical rheological model to infer ice content of rock glaciers using readily available input data, including rock glacier planar shape, surface slope angle, active layer thickness, and surface creep rate. We apply the model to infer the ice content of five rock glaciers in Khumbu and Lhotse Valleys, north-eastern Nepal. The inferred volumetric ice fraction ranges from 57.5 % to 92 %, with an average value between 71 % to 75.3 %. The total water volume equivalent in the study area lies between 10.61 and 16.54 million m3. Considering previous mapping results and extrapolating from our findings to the entire Nepalese Himalaya, the total amount of water stored in rock glaciers ranges from 8.97 to 13.98 billion m3, equivalent to a ratio of 1 : 17 between the rock glacier and glacier reservoirs. Due to the accessibility of the input parameters of the model developed in this study, it is promising to apply the approach to permafrost regions where previous information about ice content of rock glaciers is lacking.

scholarly journals Comment on "Ice content and interannual water storage changes of an active rock glacier in the dry Andes of Argentina" by Halla et al. (2021)

2021 ◽  
Author(s):  
W. Brian Whalley
Keyword(s):  
Water Storage ◽  
Rock Glacier ◽  
Melt Pond ◽  
Rock Glaciers ◽  
Ice Content

Abstract. Recently published work on water preservation in Chile assume that 'permafrost'  (cryogenic) rock glaciers are dominant. Melt pond development shows that rock glaciers are glacier-derived ('glacigenic') rather than of permafrost origin. 

Rock Glaciers and Block fields, Review and new data

1976 ◽  
Vol 6 (1) ◽  
pp. 77-97 ◽  
Author(s):  
Sidney E. White
Keyword(s):  
Ice Cores ◽  
Colorado Front Range ◽  
Front Range ◽  
Mass Wasting ◽  
Rock Glacier ◽  
Weathered Rock ◽  
Alpine Regions ◽  
Continental Divide ◽  
Glacier Ice ◽  
Rock Glaciers

Tongue-shaped and lobate rock glaciers are recognized in most alpine regions today. For the tongue-shaped, two situations emerge: those with buried glacier ice (debris-covered glaciers) called ice-cored rock glaciers, and those with interstitial ice known as ice-cemented rock glaciers. Those with ice cores are revealed by depressions between rock glacier and headwall cliff (where a former glacier melted), longitudinal marginal and central meandering furrows, and collapse pits. Ice-cemented rock glaciers ordinarily do not possess these features. As applied to 18 rock glaciers in the Colorado Front Range, 11 of 12 east of the Continental Divide are ice-cored, 6 west of the Divide are ice-cemented. The majority of lobate rock glaciers in the Colorado Front Range are on the south sides of valleys, and, except for talus, are the most voluminous form of mass wasting. All those active and above treeline have characteristics common to all rock glaciers. In addition, they originate from talus, contain interstitial ice, move outward from valley walls at 1–6 cm/yr, and transport more debris as a process of erosion than heretofore realized. Block fields and block slopes, in polar and alpine regions, are thin accumulations of angular to subrounded blocks, on bedrock, weathered rock, or transported debris. They extend along slopes parallel to the contour. Block streams are similar but extend downslope normal to the contour and into valleys. They are made of interlocked blocks without interstitial detritus, but many have finer material deeper inside. The fabric of surface blocks indicates that motion most likely occurred during a periglacial time when interstitial debris, now washed or piped out, permitted movement of the whole deposit.

Rock glacier types and their drainage systems, Grizzly Creek, Yukon Territory

1978 ◽  
Vol 15 (9) ◽  
pp. 1496-1507 ◽  
Author(s):  
P. G. Johnson
Keyword(s):  
Suspended Sediment ◽  
Sediment Load ◽  
Ice Core ◽  
Yukon Territory ◽  
Suspended Sediment Load ◽  
Rock Glacier ◽  
Vegetation Development ◽  
Recent Movement ◽  
Rock Glaciers ◽  
Ice Content

Moraine rock glaciers, talus-derived rock glaciers, and avalanche rock glaciers are described from Grizzly Creek. The main moraine rock glacier has a number of flow lobes of different ages as indicated by lichen and vegetation development. On many of these surfaces there is evidence for recent movement in the form of overridden vegetation surfaces and unstable frontal slopes. Meltwater drainage through the landform is slow, allowing precipitation of the suspended sediment load, and as resurgences do not occur for all of the inflow the possibilities of addition to the ice core or drainage below Grizzly Creek gravels are discussed. The talus-derived rock glaciers differ morphologically from the moraine forms with far greater complexity of the flow ridges but with fewer flow episodes indicated. Drainage through these forms is slow and variable and indicates percolation of meltwater over an impermeable surface within the form. Avalanche rock glaciers by contrast are relatively simple morphologically and the extension from the base of the talus is attributed to ice content derived from the avalanches.

scholarly journals Towards accurate quantification of ice content in permafrost of the Central Andes – Part II: an upscaling strategy of geophysical measurements to the catchment scale at two study sites

2021 ◽  
Author(s):  
Tamara Mathys ◽  
Christin Hilbich ◽  
Lukas U. Arenson ◽  
Pablo A. Wainstein ◽  
Christian Hauck
Keyword(s):  
Geophysical Data ◽  
Distribution Model ◽  
Permafrost Degradation ◽  
Rock Glacier ◽  
Ground Ice ◽  
Data Set ◽  
Refraction Seismic ◽  
Geophysical Surveys ◽  
Rock Glaciers ◽  
Ice Content

Abstract. With ongoing climate change, there is a pressing need to better understand how much water is stored as ground ice in areas with extensive permafrost occurrence and how the regional water balance may alter in response to the potential generation of melt water from permafrost degradation. However, field-based data on permafrost in remote and mountainous areas such as the South-American Andes is scarce and most current ground ice estimates are based on broadly generalised assumptions such as volume-area scaling and mean ground ice content estimates of rock glaciers. In addition, ground ice contents in permafrost areas outside of rock glaciers are usually not considered, resulting in a significant uncertainty regarding the volume of ground ice in the Andes, and its hydrological role. In part I of this contribution, Hilbich et al. (submitted) present an extensive geophysical data set based on Electrical Resistivity Tomography (ERT) and Refraction Seismic Tomography (RST) surveys to detect and quantify ground ice of different landforms and surface types in several study regions in the semi-arid Andes of Chile and Argentina with the aim to contribute to the reduction of this data scarcity. In part II we focus on the development of a methodology for the upscaling of geophysical-based ground ice quantification to an entire catchment to estimate the total ground ice volume (and its estimated water equivalent) in the study areas. In addition to the geophysical data, the upscaling approach is based on a permafrost distribution model and classifications of surface and landform types. Where available, ERT and RST measurements were quantitatively combined to estimate the volumetric ground ice content using petrophysical relationships within the Four Phase Model (Hauck et al., 2011). In addition to introducing our upscaling methodology, we demonstrate that the estimation of large-scale ground ice volumes can be improved by including (i) non-rock glacier permafrost occurrences, and (ii) field evidence through a large number of geophysical surveys and ground truthing information. The results of our study indicate, that (i) conventional ground ice estimates for rock-glacier dominated catchments without in-situ data may significantly overestimate ground ice contents, and (ii) substantial volumes of ground ice may also be present in catchments where rock glaciers are lacking.

scholarly journals Internal structure of two alpine rock glaciers investigated by quasi-3-D electrical resistivity imaging

2017 ◽  
Vol 11 (2) ◽  
pp. 841-855 ◽  
Author(s):  
Adrian Emmert ◽  
Christof Kneisel
Keyword(s):  
Electrical Resistivity ◽  
Internal Structure ◽  
Swiss Alps ◽  
Electrical Resistivity Imaging ◽  
Rock Glacier ◽  
Ground Ice ◽  
Resistivity Imaging ◽  
Wide Range ◽  
Rock Glaciers ◽  
Ice Content

Abstract. Interactions between different formative processes are reflected in the internal structure of rock glaciers. Therefore, the detection of subsurface conditions can help to enhance our understanding of landform development. For an assessment of subsurface conditions, we present an analysis of the spatial variability of active layer thickness, ground ice content and frost table topography for two different rock glaciers in the Eastern Swiss Alps by means of quasi-3-D electrical resistivity imaging (ERI). This approach enables an extensive mapping of subsurface structures and a spatial overlay between site-specific surface and subsurface characteristics. At Nair rock glacier, we discovered a gradual descent of the frost table in a downslope direction and a constant decrease of ice content which follows the observed surface topography. This is attributed to ice formation by refreezing meltwater from an embedded snow bank or from a subsurface ice patch which reshapes the permafrost layer. The heterogeneous ground ice distribution at Uertsch rock glacier indicates that multiple processes on different time domains were involved in the development. Resistivity values which represent frozen conditions vary within a wide range and indicate a successive formation which includes several advances, past glacial overrides and creep processes on the rock glacier surface. In combination with the observed topography, quasi-3-D ERI enables us to delimit areas of extensive and compressive flow in close proximity. Excellent data quality was provided by a good coupling of electrodes to the ground in the pebbly material of the investigated rock glaciers. Results show the value of the quasi-3-D ERI approach but advise the application of complementary geophysical methods for interpreting the results.

scholarly journals Towards accurate quantification of ice content in permafrost of the Central Andes, part I: geophysics-based estimates from three different regions

2021 ◽  
Author(s):  
Christin Hilbich ◽  
Christian Hauck ◽  
Coline Mollaret ◽  
Pablo Wainstein ◽  
Lukas U. Arenson
Keyword(s):  
Remote Sensing ◽  
Hydrological Cycle ◽  
Field Measurements ◽  
Central Andes ◽  
Rock Glacier ◽  
Ground Ice ◽  
Catchment Scale ◽  
Refraction Seismic ◽  
Rock Glaciers ◽  
Ice Content

Abstract. In view of the increasing water scarcity in the Central Andes in response to ongoing climate change, the significance of permafrost occurrences for the hydrological cycle is currently being discussed in a controversial way. The lack of comprehensive field measurements and quantitative data on the local variability of internal structure and ground ice content further enhances the situation. We present field-based data from six extensive geophysical campaigns completed since 2016 in three different high-altitude regions of the Central Andes of Chile and Argentina (28 to 32° S). Our data cover various permafrost landforms ranging from ice-poor bedrock to ice-rich rock glaciers and are complemented by ground truthing information from boreholes and numerous test pits near the geophysical profiles. In addition to determining the thickness of the potential ice-rich layers from the individual profiles, we also use the quantitative 4-phase model to estimate the volumetric ground ice content in representative zones of the geophysical profiles. The analysis of 52 geoelectrical and 24 refraction seismic profiles within this study confirmed that ice-rich permafrost is not restricted to rock glaciers, but is also observed in non-rock-glacier permafrost slopes in the form of interstitial ice as well as layers with excess ice, resulting in substantial ice contents. Consequently, non-rock glacier permafrost landforms, whose role for local hydrology has so far not been considered in remote-sensing based approaches, may be similarly relevant in terms of ground ice content on a catchment scale and should not be ignored when quantifying the potential hydrological significance of permafrost. We state that geophysics-based estimates on ground ice content allow for more accurate assessments than purely remote-sensing-based approaches. The geophysical data can then be further used in upscaling studies to the catchment scale in order to reliably estimate the hydrological significance of permafrost within a catchment.

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